I think it Freeza's final form levels (pre 50%) go more or less like withheld said, but I don't think he used his true initial level to bounce back Vegeta's super powerful blast, that was just a level used to match his speed up. His true initial level was the one used when he fought without using hands against full power base Goku.
~Freeza initial level is around post Zenkai Vegeta's level, with this latter still being a bit sure of his victory.
~Freeza increases his speed to dodge Vegeta, completely speed blitzing him and then increases his power to match his speed when bouncing Vegeta's strongest attack back.
~Freeza goes back to his initial level (the one around post Zenkai Vegeta) when underestimating Goku.
~Then Freeza power ups to the level he used to tool Vegeta and has a nice warm up against Goku, who is only warming up as well.
~Then Freeza uses his initial full level to fight base Goku full power.
Let's say Vegeta's post Zenkai power level must be at least 3 millions, based on his large superiority over 3rd form Freeza, who is unlikely to be below 2 millions:
Freeza initial 3,000,000
Vegeta Zenkai 3,000,000
Freeza (speed up and power up, kicking Vegeta's blast) 4,800,000
Goku base (initial, warming up) 4,500,000
Freeza (underestimating Goku) 3,000,000
Freeza (warm up,vs Goku) 4,800,000
Goku base (full power, warm up over) 6,000,000
Freeza (w/o hands, true initial level) 6,600,000
That's the absolute minimum imo. You could bloat up things even more if you assume Freeza didn't power down when attacking base Goku and that was the level he used to tool Vegeta:
Freeza initial 3,000,000
Vegeta Zenkai 3,000,000
Freeza (tooling Vegeta) 4,800,000
Goku base (warming up) 6,000,000
Freeza (warming up, vs Goku) 6,400,000
Goku base (full power) 8,000,000
Freeza (w/o hands) 9,000,000